, 
4 Temperature of the Terrestrial Globe. 
atmospheric strata which are condensed by their own weight, heat 
them very unequally : those which are rarest are likewise coldest, 
because they extinguish and absorb a smaller part of the rays. ‘The 
heat of the sun, coming in the form of light, possesses the property 
of penetrating transparent solids or liquids, and loses this property 
entirely, when by communication with terrestrial bodies, it is turned 
into heat radiating without light. 
This distinction of luminous and non-luminous heat, explains the 
elevation of temperature caused by transparent bodies. ‘I'he mass 
of waters which cover a great part of the globe, and the ice of the 
polar regions, oppose a less obstacle to the admission of luminous 
heat, than to. the heat without light, which returns in a contrary di- 
rection to open space. ‘The pressure of the atmosphere produces 
an effect of the same kind: but an effect, which, in the present state 
of the theory, and from want of observations compared with each 
other, cannot be exactly defined. Whatever it may be, we cannot 
doubt that the effect which should be attributed to the impression 
of the solar rays upon a solid body of very large dimensions, by far 
surpasses that which would be observed in exposing a common ther- 
mometer to the same rays. 
The radiation of the most elevated strata of the atmosphere, the 
cold of which is very intense and almost constant, has an influence 
upon all the meteorogical facts of our observation; it can be ren- 
dered more sensible by reflexion from the surface with concave mir- 
rors. The presence of the clouds which intercept these rays, miti- 
gates the cold of the nights. 
We see that the surface of the terrestrial globe is placed between 
a solid mass, the central part of which may surpass that of matter 
heated to whiteness, and an immense girdle, whose temperature is 
below that requisite for the congelation of mercury. 
All the preceding results can be applied to other planetary bo- 
dies. They can be considered as placed in a medium whose con- 
stant and common temperature is little below that of the terrestrial 
poles. This same temperature of the heavens is that of the surface 
of the most distant planets; for the impression of the rays of the 
sun, even when augmented by the disposition of the superficies, 
wold te @ too feeble to occasion sensible effects; and we know by 
‘con ition of the terrestrial globe, that, in the planets whose 
t ape peecietts pene exists upon the surface no 
1perature attributed to internal heat. 
